In the state of the art, for example, according to EP 1 785 685 A1, the different above-described zones are defined by an alternately revolving arrangement of different modules above furnace chambers that accommodate the anodes and act as a heat exchanger. The burning or firing zone arranged between the heating-up zone and the cooling zone is defined by the positioning of the burner device above the selected furnace chambers. The cooling zone accommodates the finished anodes immediately after they were fired, i.e., heated to the sintering temperature. A blower device is arranged above the cooling zone and serves for introducing air into the chambers of the cooling zone, wherein a suction device arranged above the heating-up zone conveys this air from the cooling zone into the heating-up zone via the firing zone, namely through heating flues that interconnect the chambers, and wherein this air is then conveyed in the form of flue gas from the heating-up zone through a flue gas cleaning system and released into the surroundings.
In EP 1 785 685 A1, it is proposed to convey the flue gas quantity that is withdrawn from the heating-up zone by means of the suction device and still has a temperature between 150° C. and 250° C. to a heat exchanger that should make it possible to heat the petroleum coke to approximately 150° C. prior to the moulding of the “green anodes” in a mixing and moulding module in order to ensure an improved wettability with liquid pitch during the subsequent mixing process. It is proposed that the heat exchanger for heating the petroleum coke be realized in the form of a fluidized bed or moving bed heat exchanger that needs to have a flue gas temperature of 250° C. in order to reach the desired petroleum coke temperature and is intended as a replacement for the heat exchanger in the form of a “pre-heating spiral” that was used so far in conventional systems and is operated with a heat transfer medium in the form of a heat transfer oil with a temperature of approximately 300° C.
The utilization of the method known from EP 1 785 685 A1 therefore is not possible in existing systems. In fact, the utilization of the method requires substantial modifications of the system technology for the manufacture of raw anodes. These modifications of the system technology not only include the replacement of the known pre-heating spiral with the above-described fluidized bed or moving bed heat exchanger, but also a flue gas discharge from the heating-up zone through the raw anode manufacture because it is proposed to withdraw hot air from the cooling zone of the annular anode furnace by means of a suction device and to mix this hot air with the flu gas if the temperature of the flue gas does not suffice for operating the heat exchanger. This combination of two volumetric flow rates with different temperatures for achieving the desired temperature of the heat transfer medium of the heat exchanger requires a correspondingly complex control with corresponding system technology.